Field of Invention
The present invention relates to a prosthetic device for implantation in bone, methods of planning bone removal for implantation of a prosthetic device in bone, and robotic systems for preparing a bone to receive a prosthetic device.
Description of Related Art
Conventional prosthetic implantation techniques involve resecting a pocket of material from a bone to provide a void or pocket within the bone that receives a prosthetic device. After resection of bone material is complete, the prosthetic device is implanted within the pocket. The prosthetic device is typically secured in place with bone cement.
Using the conventional techniques, undesired movement of the prosthetic device relative to the bone may occur. In particular, the pocket in the bone often includes an expansion gap that provides empty space between the prosthetic device and the remaining bone. This expansion gap may be filled or partially filled with bone cement during implantation of the prosthetic device to permit uniform or near uniform dispersion of the bone cement. FIG. 34 shows a top view of an example of a conventional prosthetic device 10 implanted in a medial condyle 12 of a tibia (the lateral condyle 14 is shown for reference). An expansion gap 16 is provided between the prosthetic device 10 and an edge of the remaining bone in the medial condyle. The expansion gap, which is typically 0.5-0.8 mm in a tibia, is exaggerated in this drawing for purposes of illustration. This expansion gap may cause the prosthetic device to be less than fully constrained, which can permit unwanted movement of the prosthetic device. Consequently, the prosthetic device may move (e.g., rotate or translate) relative to the bone when a force is applied to the prosthetic device. For example, during trial articulation of a leg, contact forces from a femoral condyle can cause unwanted movement of a tibial inlay. In addition, undesired movement can occur during final fixation as a surgeon presses against the prosthetic device to disperse the bone cement and squeeze out excess bone cement.
Using conventional techniques, it also may be undesirably difficult to properly position a prosthetic device in the pocket in the bone. For example, there can be difficulty in positioning the cup of a hip acetabulum in a desired tilt/abduction and anteversion due to difficulty in knowing exactly where a pelvis is located during total hip arthroplasty.